It is known that industrial systems such as boiler systems, cooling tower systems, heat exchanger systems and metal pretreatment systems are subject to formation of deposits on the internal surfaces that are in contact with the components circulating through the system. The cause of the deposits or scale can be from chemical reaction of the components circulating through the system with the internal surfaces of the plumbing or other areas of the system or can be caused by the components precipitating on the internal surfaces of the system. For example, in steel-based systems that circulate aqueous compositions, iron oxide or rust will build up on the interior surfaces of the system. In metal pretreatment systems using aqueous acidic solutions of metal phosphates such as zinc phosphate, the metal phosphates over time will eventually precipitate from solution and build up on the interior surfaces of the system.
The scale is often corrosive to steel plumbing and can penetrate through the steel. Leakage is often not detected because the deposit plugs the perforation. However, when the scale is removed in a cleaning operation, the perforations will be the site of subsequent leakage requiring that the system be shut down, the contents of the system removed so that the perforations can be repaired.
It would be desirable to have a method to remove scale while being able to detect leaks in the system before the system is recharged after cleaning. The present invention provides such a method and a composition for use in the method.